Diphtheria is an infectious disease caused by the bacterium Corynebacterium diphtheria, which primarily infects the throat and upper airways, and produces a toxin affecting other organs. The illness has an acute onset and the main characteristics are sore throat, low fever and swollen glands in the neck, and the toxin may, in severe cases, cause myocarditis or peripheral neuropathy. The diphtheria toxin causes a membrane of dead tissue to build up over the throat and tonsils, making breathing and swallowing difficult. The disease is spread through direct physical contact or from breathing in the aerosolized secretions from coughs or sneezes of infected individuals.
Vaccination against diphtheria has reduced the mortality and morbidity of diphtheria dramatically, however, diphtheria is still a significant child health problem in countries with poor EPI coverage. In countries endemic for diphtheria, the disease occurs mostly as sporadic cases or in small outbreaks. Diphtheria is fatal in 5 – 10% of cases, with a higher mortality rate in young children. Treatment involves administering diphtheria antitoxin to neutralize the effects of the toxin, as well as antibiotics to kill the bacteria.
Diphtheria vaccine is a bacterial toxoid, ie. a toxin whose toxicity has been inactivated. The vaccine is normally given in combination with other vaccines as DTwP/DTaP vaccine or pentavalent vaccine. For adolescents and adults, the diphtheria toxoid is frequently combined with tetanus toxoid in lower concentration (Td vaccine).
WHO recommends a 3-dose primary vaccination series with diphtheria containing vaccine followed by 3 booster doses. The primary series should begin as early as 6-week of age with subsequent doses given with a minimum interval of 4 weeks between doses. The 3 booster doses should preferably be given during the second year of life (12-23 months), at 4-7 years and at 9-15 years of age. Ideally, there should be at least 4 years between booster doses.